said by raye :

Seems to me if there is evidence of terrorist communication in a specific band of IP addresses, obtaining a warrant would not be a problem if I am a U.S. citizen. Even if I am not, getting a warrant should be trivial. Not getting one is just plain lazy, to say the least

It's employed when police have obtained a court order and an Internet service provider can't "isolate the particular person or IP address" because of technical constraints.

"In the event the intercepted communication is in a code or foreign language, and an expert in that foreign language or code is not reasonably available during the interception period, minimization may be accomplished as soon as practicable after such interception."

Downing, the assistant deputy chief at the Justice Department's computer crime section, pointed to that language on Friday. Because digital communications amount to a foreign language or code, he said, federal agents are legally permitted to record everything and sort through it later.